JP2010095743A - Oxygen pump and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an oxygen pump which works at normal temperatures and normal pressures, can easily output a high oxygen-carrying capacity, and is free from cares about the leakage of an electrolyte or the like. <P>SOLUTION: The oxygen pump includes: a porous separator 1 which is impregnated with a neutral to acidic solution containing an oxidizable type of an electrolyte which is active on a negative electrode and is auto-oxidized by oxygen and is sandwiched between a porous gas-exchangeable negative electrode 3 and a porous gas-exchangeable positive electrode 2; supplying an electric power to both electrodes 2 and 3 from an external direct-current power source through a current collection structure; and moving oxygen from a negative electrode side of gas phases in both electrode sides, which are separated from each other, to the positive electrode side. The oxygen pump is free from the cares about the electrolyte leakage or the like because of using a water-based solvent which works at normal temperatures and normal pressures, and making the porous separator impregnated with and retaining an extremely small amount of the electrolyte; also has a thin and soft structure; and can increase the oxygen-carrying capacity by increasing the area. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an oxygen pump.

  An oxygen pump forms an electrochemical cell in which an electrolyte is sandwiched between a pair of gas exchange electrodes, and directs current between both electrodes to allow oxygen to flow into the electrochemical cell from the gas phase on the negative electrode side of the gas exchange electrode. And oxygen transfer means for releasing oxygen into the gas phase on the positive electrode side of the gas exchange electrode.

  Conventionally, in this field, there are those using an aqueous electrolyte and those using a ceramic solid electrolyte. For example, Patent Document 1 discloses an oxygen pump using an aqueous electrolyte. In general, an oxygen pump using an aqueous electrolyte is excellent in that it operates at room temperature and normal pressure. However, a large amount of acidic solution or alkaline solution is held in an electrochemical cell, and there is a risk of leakage of these when it is damaged. Have. Further, in the alkaline solution, carbon dioxide in the oxygen raw material atmosphere dissolves and the carbonate precipitates, so that there is no method of using the air as the raw material oxygen. If an acidic solution is to be used, oxygen is a rather electrode-inactive substance, the negative electrode reaction is slow, and an electrode catalyst such as platinum is required. Furthermore, this catalytic reaction is the same as the reaction used for oxyhydrogen fuel cells, which is called oxygen hydrogen reduction, but under acidic conditions, oxygen is not reduced to water and produces hydrogen peroxide, which is inefficient. Is the actual situation.

There exists patent document 2 as an example using one ceramic type | system | group electrolyte. In general, those using ceramic solid electrolytes do not cause accidents such as electrolyte leakage, but they are suitable for increasing the oxygen carrying capacity by increasing the area because the operating temperature is high and the electrolyte itself is thin, hard and brittle. Absent.
Japanese Patent Publication No.59-5673 JP 2003-107043 A

  However, each of the above oxygen pumps has advantages and disadvantages, and an oxygen pump that operates at room temperature and normal pressure, can easily provide a large oxygen carrying capacity, and has no fear of leakage of electrolytes has not been found.

  The present invention has been made in view of the above points, and provides an oxygen pump that operates at room temperature and normal pressure, can easily provide a large oxygen carrying capacity, and has no problem of accidents such as electrolyte leakage. .

  The oxygen pump of the present invention provides a neutral to acidic solution of an electrolytic oxide type that is active in the negative electrode and undergoes oxygen auto-oxidation between the porous gas-exchangeable negative electrode and the porous gas-exchangeable positive electrode. The impregnated porous separator is sandwiched, and both electrodes are supplied with power from an external DC power source via a current collecting structure, and oxygen is transferred from the negative electrode side of the vapor phase isolated from the positive electrode side.

  By doing as described above, the present invention can provide an oxygen pump that operates at room temperature and normal pressure, can easily take out a large area and easily provide a large oxygen carrying capacity, and has no fear of electrolyte leakage.

  The oxygen pump according to claim 1 of the present invention is a neutral oxide of an electrolyte that is active in the negative electrode and undergoes oxygen auto-oxidation between the porous gas-exchangeable negative electrode and the porous gas-exchangeable positive electrode. A porous separator impregnated with an acidic solution is sandwiched between two electrodes, and both electrodes are supplied from an external DC power source through a current collecting structure, and oxygen is transferred from the negative electrode side to the positive electrode side of the gas phase isolated from each other Since a very small amount of electrolyte is impregnated and held using an aqueous solvent that operates at normal temperature and pressure, there is no risk of leakage of the electrolyte. Moreover, it is structurally thin and soft, and it is possible to increase the oxygen carrying capacity by increasing the area.

  The oxygen pump according to claim 2 of the present invention is a trivalent iron salt solution obtained by converting a neutral to acidic solution of a negative electrode active and subject to oxygen auto-oxidation into a trivalent iron salt solution, and provides an inexpensive electrolytic solution To do.

  The oxygen pump according to claim 3 of the present invention is obtained by adding a chloride salt to a trivalent iron salt solution, and promotes a negative electrode reaction to improve performance.

  The oxygen pump according to claim 4 of the present invention uses carbon fine powder for the positive electrode and the negative electrode, and is applied thinly to the separator to improve the adhesion between the separator and the electrode.

  The oxygen pump according to claim 5 of the present invention uses a carbon cloth for the current collecting structure, and can produce an oxygen pump having a large area of the carbon cloth and can increase the oxygen carrying capacity. Furthermore, by pulling out the fibers of the carbon fiber cloth, connection with an external power supply circuit becomes easy.

  The oxygen pump according to claim 6 of the present invention is obtained by molding the laminated film-like separator, both electrodes, and the peripheral ends of the current collecting structure with an adhesive, and the escape of gas in the surface direction between the positive electrode and the negative electrode Restricts the entrainment of gas.

  The oxygen pump according to claim 7 of the present invention is formed by impregnating a neutral to acidic solution of an electrolyte that is negative electrode active and undergoes oxygen auto-oxidation to form a porous separator, and after drying the porous separator, This is a manufacturing method in which an electrode and a current collecting structure are added to a porous separator, and the oxygen pump structure is assembled, and then the electrolyte solution is regenerated by absorbing water with water vapor. It becomes.

  Embodiments of the present invention will be described below. In addition, this invention is not limited by this description.

(Embodiment 1)
FIG. 1 shows a cross-sectional view of an oxygen pump, in which a positive electrode 2 and a negative electrode 3 configured by applying fine carbon powder are arranged on both sides of a separator 1 impregnated with an electrolyte solution, and a carbon cloth is closely attached to the outside. By forming the positive-side current collecting electrode 4 and the positive-side current collecting electrode 5, a laminated structure is formed, and an adhesive is impregnated and built up at the end portion in the surface direction to connect and integrate the structures as a mold 8. . The positive electrode side electrode takeout part 6 and the negative electrode side electrode takeout part 7 to the outside draw the carbon fiber of the carbon cloth from the mold 8 and connect it to an external DC power source (not shown).

  The separator 1 uses an aqueous solution of ferric chloride and calcium chloride as the application screening cell electrolyte. The mixing ratio is 0.2 to 2 equivalent to anhydrous ferric chloride and 4 to 15 water per calcium chloride anhydride. After being applied to the separator 1, it is dried and laminated with both electrodes and both final electrodes, and a mold 8 is formed and integrated by impregnating and building up an adhesive at the end portion in the surface direction. In addition, it is difficult to make a mold with a wet separator that is not dried.

  In the above configuration, the mixture of ferric chloride and calcium chloride on the separator has strong deliquescence, absorbs water vapor from the atmosphere, falls within a water molar ratio of 4 to 15, and returns to its original wet state. Within this range, the electrolyte behaves as a non-volatile solution and does not dry out. In addition to the separator, the surrounding carbon fine powder or carbon cloth holds the aqueous solution, so that it does not spill and leak, and is not lost or soiled.

  In a steady state operation of the oxygen pump operation, when a DC voltage is applied from an external DC power source, the current is transmitted from the positive electrode side electrode take-out unit 6 to the positive electrode 2 through the positive electrode side collecting electrode 4, Oxygen is generated by exchanging electric charge with the electrolyte solution on the powder surface, and then transmitted through the electrolytic solution impregnated in the separator 1 by ionic conduction to reach the surface of the carbon fine powder of the negative electrode 3, and the electric charge is exchanged again to perform electrolysis. Oxygen is taken into the liquid, and further returns to the external DC power source via the negative electrode side collecting electrode 5 and the negative electrode side electrode take-out part 7, so that a closed circuit can be formed as a whole. At this time, gaseous oxygen is taken into the electrolytic solution from the negative electrode-side gas phase 10 on the surface of the fine carbon powder of the negative electrode 3, is transmitted through the electrolytic solution in accordance with ionic conduction, and returns to oxygen on the surface of the fine carbon powder of the positive electrode 2. Then, it is discharged into the positive electrode side gas phase 9 and the function of oxygen transfer as an oxygen pump is exhibited.

  More specifically, in accordance with energization, trivalent iron ions of ferric chloride on the negative electrode surface receive electrons from the negative electrode and are reduced to divalent iron ions.

Fe ₃ ⁺ + e ⁻ → Fe ₂ ⁺
Subsequently, the divalent iron ions are auto-oxidized with oxygen to return to trivalent iron ions, and water is generated from the hydrogen ions in the solution, and oxygen is taken into the electrolyte.

4Fe ₂ ⁺ + O ₂ + 4H ⁺ → 4Fe ₃ ⁺ + 2H ₂ O
Therefore, in the entire reaction of the negative electrode, oxygen and hydrogen ions receive electrons from the negative electrode, and water is generated.

O ₂ + 4H ⁺ + 4e ⁻ → 2H ₂ O
Even if this entire reaction of the negative electrode is carried out without the auto-oxidized divalent iron ions, oxygen is quite inactive and hardly reacts with the negative electrode. When a catalyst such as platinum is supported on the negative electrode, it reacts. In this case, hydrogen peroxide is first generated.

O ₂ + 2H ⁺ 2e ⁻ → H ₂ O ₂
Next, hydrogen peroxide and hydrogen ions receive electrons from the negative electrode to produce water.

H ₂ O ₂ + 2H ⁺ + 2e ⁻ → 2H ₂ O
However, this latter reaction does not proceed easily, and usually hydrogen peroxide accumulates, resulting in poor reaction efficiency. In the present invention, oxygen can be efficiently taken in by introducing divalent iron ions to be auto-oxidized. Since iron ions are electrode active, it is easy to receive charges from the electrodes. Trivalent iron ions are an oxidized form of divalent iron ions that are auto-oxidized.

  On the other positive electrode surface, water gives electrons to the positive electrode to generate oxygen and hydrogen ions.

2H ₂ O → O ₂ + 4H ⁺ + 4e ⁻
Here, calcium chloride not directly involved in oxygen transport also has several functions. First, chlorine ions act to promote oxygen auto-oxidation of divalent iron ions, and oxygen uptake at the negative electrode 3 is accelerated. In this embodiment, iron ions are also supplied in the form of chloride. However, by adding calcium chloride, oxygen autooxidation of divalent iron ions is further accelerated. Secondly, the presence of a large amount of calcium ions suppresses the generation of hydrogen gas from the negative electrode. Calcium ions are electrically adsorbed on the surface of the negative electrode, and the pH of the calcium ions keeps the electrode surface on the alkali side, so that the hydrogen generation equilibrium potential is lowered and hydrogen gas is hardly emitted. Third, the solubility of iron involved in the reaction can be increased. Since it is impossible to impregnate the separator with an iron salt that does not dissolve, if the iron salt is charged at a high concentration, the solubility must be increased. Calcium chloride co-dissolves with ferrous chloride and helps dissolve ferrous chloride. Fourth, calcium chloride is a source of chloride ions. Trivalent iron ions tend to form insoluble hydroxides, which irreversibly change to iron oxide (iron trioxide), but when high concentrations of chlorine ions are present, the chloride ions become iron. Since it coordinates with ions and competes with hydroxide ions, irreversible iron oxide production can be prevented.

  The separator 1 includes a porous membrane having gaps penetrating the front and back of many names, materials, and manufacturing methods such as a battery separator, an electrolytic partition, an ultrafiltration membrane, a filter paper, and a nonwoven fabric, and these can be used. However, the separator 1 of the present invention has a function of performing gas separation by blocking the gas phase communication on the negative electrode side and the positive electrode side, in addition to insulating the electron conduction between both electrodes. The gap must be filled with electrolyte solution and not allow gas to pass through. For this purpose, a material that is water-repellent and does not repel the electrolyte is not acceptable, and a water-repellent material such as polyethylene or polytetrafluorocarbon cannot be used unless it is hydrophilized. In addition, a material having a large opening is desirable even if it is a hydrophilic material, since the liquid runs out and the gas phase communicates. The purpose can be achieved if the film has an opening of about 3 micrometers or less.

  Carbon black, graphite carbon powder, activated carbon powder, etc. can be used as the carbon fine powder of the electrode material of the positive electrode 2 and the negative electrode 3. A fine layer that does not peel off when applied to the separator 1 is preferable, and its particle size is 10 micrometers or less. Carbon black acetylene black is favorable because it is available in stable and fine particulate form. The carbon fine particles have good conductivity, and an electrode in close contact with the separator can be easily formed.

  Carbon cloth is usually a fabric in which a bundle of carbon fibers is plain woven. Carbon fibers are classified into raw materials by PAN, pitch, rayon, etc., and there are various mechanical properties such as elastic modulus. Absent. Carbon cloth is soft and strong, can make a large area oxygen pump, and can increase oxygen carrying capacity. Further, the carbon fiber bundle of the carbon cloth is pulled out and bound with a crimp terminal or the like, and the terminal is taken out and can be easily connected to an external power supply circuit.

  In the oxygen pump of the present invention, the laminated film-like separator 1, the two electrodes 2 and 3, and the peripheral ends of the current collecting structure are molded with an adhesive, and the escape of gas in the surface direction and the gas between the positive and negative electrodes Regulate wraparound. As the paste used for this purpose, rubber paste in which rubber such as neoprene is dissolved in a solvent, silicone sealing agent, etc. can be used as long as it is resistant to the water of the electrolytic solution. The mold regulates escape of gas in the surface direction and gas sneaking between the positive and negative electrodes.

  As described above, the oxygen pump of this embodiment uses an aqueous solvent that operates at normal temperature and pressure, and an extremely small amount of electrolyte is impregnated and held, so that there is no problem of accident such as leakage of the electrolyte. Structurally thin and soft, it is possible to increase the oxygen carrying capacity by increasing the area.

  Hereinafter, experimental examples will be described.

The oxygen pump used in the experiment has the configuration shown in FIG. 2, the polyethylene hydrophilized separator 1 has a thickness of 0.38 mm (manufactured by Nippon Sheet Glass Co., Ltd.), the electrodes 2 and 3 are acetylene black (manufactured by Wako Pure Chemical Industries, Ltd.), Carbon cloth (manufactured by Mitsubishi Rayon Co., Ltd.), mold 8 is a silicone sealant (manufactured by Shin-Etsu Chemical Co., Ltd.), has a circular effective diameter of 30 mm (effective area of 7.0 square centimeters), and a thin film micro flow meter is connected to the gas outlet 12. The flow rate can be observed. The experiment was conducted at room temperature (about 25 ° C), 2.1 V was applied, 1.4 ampere of current flowed, 0.044 ml / s of gas flowed out of the positive electrode, and the stoichiometry of current and gas flow rate. Relationship was confirmed.

  As described above, the oxygen pump of the present invention operates at room temperature and normal pressure, can easily provide a large oxygen carrying capacity, and has no problem of accidents such as electrolyte leakage. It can be applied to fields such as combustion, fish farming, and medicine, foods that require low oxygen conditions, and food storage.

Sectional drawing which shows the structural example of the oxygen pump in Embodiment 1 of this invention. Sectional view showing an experimental example of the oxygen pump

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Separator 2 Positive electrode 3 Negative electrode 4 Positive electrode side current collection electrode 5 Negative electrode side current collection electrode 6 Positive electrode side electrode extraction part 7 Negative electrode side electrode extraction part 8 Mold 9 Positive electrode side gas phase 10 Negative electrode side gas phase 11 Positive electrode side case 12 Gas outlet

Claims (7)

Between the porous gas-exchangeable negative electrode and the porous gas-exchangeable positive electrode, a porous separator impregnated with a neutral to acidic solution of the oxide oxidation type that is active in the negative electrode and undergoes oxygen auto-oxidation An oxygen pump that sandwiches and feeds both electrodes from an external DC power source via a current collecting structure, and moves oxygen from the negative electrode side to the positive electrode side of the vapor phase isolated from each other. 2. The oxygen pump according to claim 1, wherein the neutral to acidic solution of the electrolyte that is active in the negative electrode and undergoes oxygen auto-oxidation is a trivalent iron salt solution. The oxygen pump according to claim 2, wherein a chloride salt is mixed and added to the trivalent iron salt solution. The oxygen pump according to claim 1, wherein the positive electrode and the negative electrode are fine carbon powder. The oxygen pump according to claim 1, wherein the current collecting structure is a carbon cloth. The oxygen pump according to claim 1, wherein the peripheral ends of the laminated film separator, both electrodes, and the current collecting structure are molded with an adhesive. The porous separator is impregnated with a neutral to acidic solution of an electrolyte that is active in the negative electrode and subjected to oxygen auto-oxidation to form a porous separator. After the porous separator is dried, the electrode is collected on the porous separator. A method for producing an oxygen pump in which an electric structure is added and an oxygen pump structure is assembled, and then an electrolyte solution is regenerated by absorbing water with water vapor.